Traditional database systems provide a database catalog having metadata in which definitions of database objects such as base tables, views (virtual tables), synonyms, value ranges, indexes, users, and user groups are stored. The database catalog is typically within the database system. The database system must retrieve information from the database catalog to perform database operations. The database catalog may also be stored in a separate catalog server.
Traditional database systems also provide locks on database operations, where a lock is acquired for a portion of an operation, and the lock is dropped when a portion of the operation is complete. That is, locks are acquired, dropped, and reacquired during the course of performing a database operation.